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MultiTouchBoard

Introduction:

This is a walkthrough on how we are creating the MultiTouchBoard. The basic idea is a device that can sense the x and y coordinates when touched with anything conductive. The way this is implemented is through some sort of square conductive material (in our case conductive paint), a micro controller (in our case a teensy 2.0), and some sort of conductive input (in our case a magnet soldered to the input of the teensy through a wire). By attaching four outputs to the four sides of the board (let's say North, South, East, and West for ease of explanation) and turning North to ground, South to 5V, East to ground, and West to ground, for example, any point the input touches will cause a voltage division, because the input is conductive, so the voltage measured at the input will give an x-location. Then switching the outputs so that North is ground, South is ground, East is ground, and West is 5V, similarly the y-location can be found. Using this sampling method any counductive input can be converted to an x and y location.

Place a strip of copper tape on all four sides of the wooden cutting board. Each piece of copper tape should not touch any of the tape on a different side.

Place an additional piece of copper tape from some point on the currently placed tape perpendicularly so that it runs from the side to the underbelly of the cutting board. These will will be the hookups for the outputs of the microcontroller. We did it on the right hand corner of each side when the board is facing up.

Finished on all four sides.

3. Painting the board

Paint the board using the conductive paint. We first placed painters tape on each side in order to make the board look cleaner when finished.

Let dry for at least 12 hours.

Part 2: Diodes

1. Materials

1x soldering iron
1x solder
a lot of diodes

2. Setting up the Diodes

What we are doing here is soldering diodes from the copper tape on the side of the board to the conductive paint on the top of the board. If we neglected the diodes and connected the copper tape and conductive paint directly all the current would not all flow through the conductive surface as we would like. A lot of the current would flow through the copper tape, which would make it very hard to calculate x and y loactions of inputs.

The main thing to remember here is to remember that diodes are directional so if the anode side of the diodes is soldered to the North side of the board make sure that the catthode side of the diodes is soldered to the South side.